nilfs2: super root size should change depending on inode size

The size of super root structure depends on inode size, so
NILFS_SR_BYTES macro should be a function of the inode size.  This
fixes the issue.

Even though a different size value will be written for a possible
future filesystem with extended inode, but fortunately this does not
break disk format compatibility.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index 8768c46..bd8678f 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -107,7 +107,7 @@
 #define NILFS_SR_DAT_OFFSET(inode_size)     NILFS_SR_MDT_OFFSET(inode_size, 0)
 #define NILFS_SR_CPFILE_OFFSET(inode_size)  NILFS_SR_MDT_OFFSET(inode_size, 1)
 #define NILFS_SR_SUFILE_OFFSET(inode_size)  NILFS_SR_MDT_OFFSET(inode_size, 2)
-#define NILFS_SR_BYTES                  (sizeof(struct nilfs_super_root))
+#define NILFS_SR_BYTES(inode_size)	    NILFS_SR_MDT_OFFSET(inode_size, 3)
 
 /*
  * Maximal mount counts